There are many applications in which it is desirable to seal a secure enclosure to prevent an unauthorized access to the secure enclosure contents. As used herein, the term “secure enclosure” includes, but is not limited to, shipping containers used in international and/or intermodal commerce (e.g. 40 TEU container), electric power meters and transmission or distribution control boxes, traffic signal control boxes, telephone equipment controllers or other industrial equipment enclosures, commercial trucks, airborne containers, commercial vehicle trailers; military vehicles having access hatches; and facilities having inspection or other access ports including hazardous materials storage facilities, process facilities such as electric power generation, chemical and petrochemical, refinery, food, pharmaceutical and fermentation facilities to which access control is desirable for control, safety or security purposes.
In the past, the primary concern was the theft of secure enclosure contents. More recently, secure enclosure sealing has been prescribed to prevent the unauthorized addition of contraband including weapons and illegal drugs (e.g. to the contents of a shipping container). These concerns are heightened for containers that are shipped internationally. One protocol for preventing an unauthorized access to a secure enclosure involves sealing the secure enclosure at the point of origin followed by an inspection of the secure enclosure seal upon arrival at the shipping destination to ensure that the interior of the secure enclosure has not been accessed in-route.
Heretofore, mechanical seals have been primarily used in the commercial transportation industry to verify container integrity during transport and storage. Mechanical seals have also been used in a number of industrial applications, for example, to verify access control to industrial enclosures such as electrical equipment housings and NEMA enclosures. Typically, a mechanical seal consists of one or more small loops of either plastic or metal that are affixed to either the door hasp or closing mechanisms of a secure enclosure. For example, a mechanical seal can be installed when responsibility for the cargo in a shipping container transfers to a motor carrier. Generally, each mechanical seal contains an identification number imprinted on the seal to prevent the unauthorized replacement of a broken seal. In the case of a shipping container, upon arrival at the point of destination, the mechanical seal must be visually inspected to ensure the integrity of the container contents. This manual inspection can be time consuming and labor intensive, especially at a large warehouse or receiving terminal where a large quantity of sealed containers must be received and inspected each day.
One particularly burdensome requirement associated with mechanical seals is the requirement that an inspector obtain close access to a particular location on each container (e.g. the hasp) to make an adequate inspection. Close proximity inspections disallow regular, in-transit and mobile monitoring of seal status because seals cannot be monitored remotely.
Electronic seals have been heretofore suggested to expedite the inspection of sealed containers. For example, U.S. Pat. No. 5,656,996 entitled “Electronic Security Bonding Device” which issued on Aug. 12, 1997 to Houser discloses a container seal that can be read from a remote location to verify the integrity of the container seal. In greater detail, Houser '996 discloses an electronic seal that is attachable to the hasp of a shipping container, a commercial vehicle trailer or a commercial truck. The seal disclosed by Houser '996 includes a conductive loop that is placed through the container or trailer or truck door hasp and is electronically monitored by a sensing means. A break in the loop or an absence of the seal can be sensed at a remote location using a reader. At least in theory, the seal disclosed by Houser '996 can be used to verify quickly the integrity of a large number of containers from a remote location.
Unfortunately, the electronic seal disclosed by Houser '996 presents a number of disadvantages, primarily due to the seals' dependence on a loop structure to sense container tampering. One such disadvantage arises because the seal must typically be installed on a door hasp or over the handles between opposed doors. Because of this installation, the seal is vulnerable to tampering modes in which both doors are simultaneously removed from the container. For example, cases have been reported in which the doors of a commercial trailer have been lifted off their hinges while the door hasp remains undisturbed relative to the doors. After the contents of the trailer were accessed, the doors were replaced, with the door hasp and seal left intact.
Another disadvantage associated with a loop-type seal that is installed on a door hasp is the somewhat limited ability to receive a signal from the seal by a remotely positioned reader. For example, if the signal is communicated via an optical signal (e.g. barcode), a short range line-of-sight between seal and reader is typically required. Also, a line-of-sight between seal and reader may also be required when RF signals are used. Because of this requirement, poor positioning of an electronic seal's transmitting antenna on a container can result in poor signal transmission to the remote reader. More specifically, shipping containers, which are typically metal, tend to reflect and attenuate the transmitted signal, reducing the signal's power. Thus, signals originating from poorly positioned transmitters are often difficult to receive and it is often difficult to separate effectively the weak signal from other noise in the environment.
Another disadvantage associated with a loop-type seal is that its practical use is limited to secure enclosures having specific structures that can be sealed using a loop (e.g. hasps and opposed door handles). Although secure enclosures could be modified to accommodate a loop-type seal, such a modification may be costly. In addition to the above-described disadvantages, loop-type electronic seals are complicated and relatively expensive. In fact, most hasp-mounted electronic seals have been designed to be re-usable to justify their relatively high cost. Such re-use would typically require carriers and other users to maintain a costly and complex asset management system to control their inventory of seals and has therefore been a major impediment to widespread adoption in industries such as commercial freight movement.
In light of the above, it is an object of the present invention to provide a seal system suitable for the purposes of sealing a secure enclosure and electronically monitoring the integrity of the seal from a remote location. It is another object of the present invention to provide a secure enclosure seal system that cannot be easily bypassed or circumvented. It is yet another object of the present invention to provide a secure enclosure seal system that can be located on the secure enclosure at an advantageous position to increase the ability of a remote reader to obtain an indicating signal from the seal. It is still another object of the present invention to provide a secure enclosure seal system for use on secure enclosures that cannot be sealed using a loop-type seal because the enclosure lacks specific structures such as a hasp. Yet another object of the present invention is to provide a secure enclosure seal system that is easy to use, relatively simple to implement, and comparatively cost effective.